Nerve agents environmental persistence

GD is likely to undergo hydrolysis in most soils. As noted above, the rate of hydrolysis will be dependent upon temperature and pH. According to Morrill et al. (1985), evaporation is the primary mechanism for the loss of the GA and GB nerve agents from soil. Although the G agents are liquids under ordinary environmental conditions, their relatively high volatility and vapor pressure permits them to be disseminated in vapor form. Because of this volatility, GD is not expected to persist in soils. 

M. L. Davisson. 2004. Investigating the affinities and persistence of VX nerve agent in environmental matrices. Chemosphere 57(10) 1257-64. 

Environmental Fate. The primary degradation mechanism for nerve agents in the environment is hydrolysis to the corresponding alkyl methylphosphonate, followed, for most of the agents, by slow hydrolysis to methyl phosphonic acid. The alkyl methylphosphonates may persist for years in the environment. Degradation or decomposition in soil may be faster than in water as a result of the variety of available processes and catalysts. 

Once chemical agents are fully dispersed, they do not tend to persist in the environment because of their high chemical reactivity, particularly with water (hydrolysis). However, in extremely dry desert climates, they can persist for considerable periods of time (U.S. Army, 1988). The major environmental degradation products of nerve and mustard agents have recently been assessed and their persistence and toxicity evaluated. A potential hydrolysis product of VX (S-(2-diisopropylaminoethyl) methylphosphonothioic acid [EA-2192]) is a degradation product expected to display a high level of mammalian toxicity. Some mustard partial hydrolysis products are also toxic (Munro et al., 1999). 

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